This invention relates to a device for repeatably scribing a scratch having sharply defined dimensions on the interior surface of a nuclear reactor fuel rod tube. More particularly, lengthwise the scratch runs parallel to a line drawn through the axis of the fuel rod tube and is in the shape of an arc, and widthwise the scratch is V-shaped.
It is becoming increasingly important from a safety view-point to determine how long a fuel rod tube will last in reactor use (failure time) with defects such as scratches on its interior surface. There are two methods to determine failure time, by the use of destructive testing and by the use of formulas which are well known in the art. The correlation of these two methods is essential to developing a reliable, cheap and fast way of accurately predicting failure time.
Destructive testing involves intentionally scoring the interior surface of a fuel rod tube with a known defect and then subjecting the tube to a hydraulic test of about 10,000 psi at reactor temperature until failure occurs. The shape of the scratch is important so that the dimensions of the scratch can be plugged into appropriate formulas which are well known in the art to calculate stress intensity of cracks in the fuel rod tubes so that failure time can be predicted. Lengthwise the scratch must run parallel to a line drawn through the axis of the fuel rod tube and be in the shape of an arc, and widthwise the scratch must be V-shaped.
A device was necessary for scribing a scratch on the internal surface of a fuel rod tube with the above discussed shape which can repeatably scribe a scratch having sharply defined dimensions. The device must also be adaptable for use in a cave by remote control handling devices since testing must be done upon irradiated as well as nonirradiated fuel rod tubing. Several devices have been developed for scribing defects in fuel rod tubes. However, these are time-consuming, expensive, and do not repeatably scribe scratches with well defined dimensions.
It is therefore an object of the present invention to provide a device which can repeatably scribe a scratch having sharply defined dimensions on the interior surface of a fuel rod tube. Lengthwise the scratch runs parallel to a line drawn through the axis of the fuel rod tube and is in the shape of an arc, and widthwise the scratch is V-shaped.
It is a further object of the present invention to provide a device for scribing a scratch on the interior surface of a fuel rod tube in a relatively inexpensive and non-time-consuming manner.
It is a further object of the present invention to provide a device for scribing a scratch on the interior surface of a fuel rod tube which is adaptable for use in a cave by remote control handling devices.